DE2729277A1 - METHODS FOR TREATMENT OF SLUDGE OR ASH, IN PARTICULAR OF SEWING SLUDGE OR SEWING SLUDGE ASH - Google Patents

Description

The invention relates to a method for treating sewage sludge or sewage sludge ash, which contains mineral fertilizer components that are poorly available for plants.

When cleaning industrial or municipal wastewater in Clarification plants, for example the cleaning of organically contaminated Wastewater after the activated sludge process, a sewage sludge is produced as an end product, which is usually either burned, thickened or mixed with household waste will. The value of this sewage sludge as a fertilizer is impaired by the fact that it contains rrii ^ pralischen fertilizer components, especially the phosphate compounds, such as iron, aluminum or calcium phosphates, on green their chemical bond for the plants as a fertilizer does not are fully available, d. That is, the plants are only incomplete in the d Able to absorb these mineral fertilizer components.

The invention is based on the object of developing a method which makes it possible to remove sewage sludge or sewage sludge machines to produce high quality fertilizers.

This object is achieved according to the invention in that the Sewage sludge or the sewage sludge ash in the presence of an or subject several disintegrating agents to a high temperature treatment j / ird, the name of the fertilizer that is not available for plants components are converted into plants available.

Through the organization of the sewage sludge or you l · '.! ; ir; i: i. :; »: -. FTi: ii; i: luj with a suitable additive. '. It tel, which is accompanied by the: fiji nif · l'f lan? I; ii not available fertilizer components a high temperature treatment reacts chemically such that substances are produced, which are available for the plants as Dünqernittel now, it is possible from a small amount of precious sewage sludge or sewage sludge ash a high-quality fertilizer testify to it.

809881/0487

ORIGINAL INSPECTED

With regard to the phosphate compounds contained in the sewage sludge, such as iron, calcium and aluminum phosphates, particularly substances such as Na ₃ CO ₃ , CaO, Ca (OH) ₂ / MgO and MgSO ₄ are suitable as digesting agents. For example, when using Na _{2 CO as a disintegrating agent, the plant-available CaNaPO 4} can be obtained from iron, calcium and aluminum phosphates, which are poorly available to plants. When MG salts are used as the disintegration agent, the plant-available Mg ^ (PO ₄ I _{2) is produced} , while the use of CaO as the disintegration agent produces calcium silicophosphates that are readily available to plants, since the sewage sludge or its ashes always contain high amounts of SiO ".

The necessary addition of these digesting agents varies greatly depending on the composition of the sewage sludge or sewage sludge ash and is usually between 5 and 40 % based on the mixture. For example, when using a sewage sludge with 22 % total P ₂ O ₁ . a degree of digestion of 73 % in the ash by adding 20 % soda; in the case of a sludge with a P ₂ O content of 8% in the ash, 5.7 % soda is sufficient for a degree of digestion of 74%.

According to the method according to the invention, both sewage sludge as well as sewage sludge see the high temperature treatment in the presence are supplied by digesting agents. Here, sewage sludge ash is both that of sewage sludge incineration and Also to be understood as the solid residue that occurs during the gasification of sewage sludge to generate a fuel gas. The treatment the sewage sludge ash can take place in the melt, preferably in a so-called melting chamber furnace, with the mass transfer is higher in the melt than in the solid phase, which leads to a shortening of the reaction times.

808681/0487

It has been shown that the efficiency of the digestion is greatest at reaction ^{temperatures between 600 and 1,400.degree.} C., preferably between 900 and 1,200.degree.

The high temperature treatment of the sewage sludge or the Sewage sludge ash can also be carried out in other furnaces, for example in rotary drum furnaces, rotary tube furnaces, muffle furnaces or fluidized bed furnaces.

The treatment has proven to be particularly effective. of sewage sludge or sewage sludge ash in a fluidized bed furnace, in which all reactants are kept in a highly turbulent state of motion The heat transfer between the reactants is also great, so that with relatively short residence times (about 2-20 seconds) can be driven.

Another possible method is to briquette the sewage sludge ash to be treated with the addition of disintegrating agent and to mix the briquettes with hot iron and steel slag for high temperature treatment. The hot slag serves as a heat supplier for the chemical. Implementation in the briquette between ash and, for example, soda. The heat content of the slag is transferred to the briquettes to be broken down, so that the supply of external heat can advantageously be dispensed with. Depending on the heat loss of the slag, the z. B. is due to radiation, can by means of 1 ton of slag to from 0.7 to 0.8 t ash briquette to a temperature of about 800 ⁰ C brought \ rerden.

808881/0487

With this process variant, two less relevant waste materials can be removed with the help of previously unused and Therefore, a large amount of lost heat energy can be used for combine agriculture with valuable fertilizers.

There are several possibilities for adding the digestion to the sewage sludge to be treated 71.1 : The digestion, if it is insoluble in water, can already be added during the cleaning of the 3bv / äss «r; but it can also be added later to the already thickened h? w. a'JSqef attracts or thermally conditioning sewage sludge is added, or it is introduced directly into the high-temperature treatment zone. In sewage treatment plants that are already equipped with an incineration plant for the sewage sludge, it proves to be expedient to also introduce the digestion agent into the incineration plant and thus carry out the conversion of the fertilizer components that are not available to plants into those that are not available to plants on the spot. In this case, the additional investment outlay for carrying out the method according to the invention is particularly low.

The invention is described below on the basis of exemplary embodiments explained in more detail. Show it

- Examples 1 to 6 with different conclusions

experiments carried out. The specified lemon acid solution is

possibility (2 S citric acid) of the digestion mass a MaO for |

the plant availability of the fertilizers obtained,

808881/0407

- Table 1 the result of two vegetation tests,

- the figure shows a schematically illustrated embodiment game of a preferred variant of the method for implementation of the erf i ndtjnq ^ qnmnOcn procedure.

Example 1;

ι ·

85 parts of sewage sludge ash (solubility in 2 S> citric acid 0.5 % (pH 3.4)) are intimately mixed with 15 parts of kieserite (MgSOa) and treated at 1200 ° C. in a rotary kiln. Ce results in a digestion mass which, with 21.5 % total PO _{5, has} a relative solubility in citric acid of 71 *

having. >

Example 2;

71 parts of ash are intimately mixed with 29 parts of CaO .; and treated in a muffle furnace at 1200 ⁰ C. The result is a digestion mass which, at 16.1% total P 0, has a relative solubility in citric acid of 87 % .

Example 3:

82 parts of ash are intimately mixed with 18 parts of sodium carbonate ond in a rotary kiln at 900 ⁰ C treated. The result is a digestion mass which, at 19.8 % total P-Oc, has a relative solubility in citric acid of 95 % .

Example 4;

80 parts of ash intimately mixed with 16 parts of sodium carbonate and 4 parts of CaO and treated at 950 ⁰ C. The result is a digestion mass which, at 18.9% total P ₂ O _{5, has} a relative solubility in citric acid of 92 % .

808461- / 0487

ORIGINAL INSPECTED

Example 5:

50 parts of sewage sludge with an H ₂ O GBhIaIt of 50 % and one

P _? Oc content in the dry matter of 7.3 % is 1.8: Parts of soda thoroughly mixed and with increasing temperature up to ^:

Burned 950 C. The result is a Christian open-minded;

Ash with a relative solubility of I at 18.7% total PO ₅

in citric acid of 73 % . ■

Example 6; i

80 parts of ash and 20 parts of soda are formed into briquettes and embedded in hot LC slag in a ratio of 25% briquettes + 75 % LD slag and stored for 2 hours. The result is a digested briquette mixture with 19.1 % total P ₂ Oj; at 100 % Tel. solubility. The joint grinding of LD slag + briquette resulted in 9.2 % total P ₂ O with a solubility of 78 %. The LD slag alone showed 3.7 % total P ₂ O ₅ with a solubility of only 46 %.

In Table 1 is an example of the success of the invention ■ according to the procedure, the result of two vegetation tests ί

shown. This shows that sewage sludge ash digested with soda develops the same plant activity as the standard fertilizer Thomas phosphate. j

The figure shows a method variant for carrying out the method according to the invention. Here, sewage sludge of any origin is used, the mineral sludge for plants is not. available fertilizer components, such as B. iron, aluminum; and contains calcium phosphates, fed via a line 1 to the system and intensively in a mixing system 2 with a suitable digesting agent, such as. B. Na «CO ,, or MgO, which one ^! via a line 3 and a metering device k to the mixer:

eO888VIH87

INSPECTED

container is .zugeleitet 2, mixed, then the mixture of sewage sludge and digesting agent is fed by means of a screw conveyor 5 in a fluidized-bed furnace 6 where it is burnt at a temperature of about 900 ⁰ C. The combustion air is the fluidized bed furnace 6 via a line 7 and a preheater 8 and the required fuel, e.g. B. gas or oil, fed via a line 9.

By adding the above-mentioned disintegrating agents to the sewage sludge, a chemical conversion of the sludge contained in the sewage sludge takes place in the course of the incineration of the sludge, Plant-available phosphat compounds instead of phosphate compounds that are now available to plants and are therefore particularly suitable as fertilizers.

The resulting in the fluidized bed furnace 6 reaction products such as Exhaust gas, sand and ash, which contain the digested mineral fertilizer components, are passed through a line 10 withdrawn, cooled in a heat exchanger 11 or by admixture of air and then in a cyclone separator 12 one Subjected to coarse disassembly. The solids separated here, essentially sand and ash, are removed via a line 13 Derived from the cyclone, while the still slightly contaminated exhaust gas is fed via a line 14 to a filter 13 and in this is subjected to a fine cleaning. The cleaned exhaust gas leaves the filter via a line 16, while in the filter separated fine ash is withdrawn via a line 17.

The ashes occurring in the cyclone 12 and in the filter 15 can as a result of the conversion, carried out in accordance with the invention, of the fertilizer components which are not available to plants into those which are available to plants as high-quality fertilizer after appropriate grinding can be reused.

008881/0487

ORIGINAL INSPECTED

jelle 1

Phospha tw lrkunq from thermally digested sewage pipe ash

Bredeney clay soil _with pH 5.5

without phosphate Thoma s phos phat (standard)

Vers.Charge 81/76

85 tons of ash + 15 tons of soda

^ Sandy soil

PH

without phosphate

Thomas phosphate

(Default)

Vers.Charoe 81/76

85 tons of ash + 15 tons of soda

'- ^P 2 ° 5 total

O, 3 0.6

0.3 0.6

O. 3 0.6

0.3 0.6

Total yield

in q Tr.M./Vessel

Oats + so. flower

58.6

96.6

111.4

97.9 106.5

49.4 68.9 93.3

72.9 89.4

Total withdrawal

in mg P ₂ O ₅ / vial

228.1 350.9 394.9

387.8 410.5

Q)

128.7 189.6 277.1

181.0 245.2

Claims (9)

Claims 1. A method for the treatment of sludge or ashes, in particular sewage sludge or sewage sludge ash, which contains mineral fertilizer components that are poorly available for plants, characterized in that sludges
or ash, in particular the sewage sludge or sewage sludge ash, is subjected to a high-temperature treatment in the presence of one or more disintegrating agents
which converts the fertilizer components that are poorly available to plants into those that are available to plants. 2. The method according to claim 1, characterized in that the
Sewage sludge ash is melted and treated with
the disintegration agent takes place in the melt. 3. The method according to claims 1 or 2, characterized in that that the high-temperature treatment at temperatures between 600 and 14OO ° C, preferably at temperatures between 900 and 1200 ° C, is carried out. 4. The method according to any one of claims 1 to 3, characterized in that that the disintegration agent is added to the sewage sludge or sewage sludge ash before the high-temperature treatment will. 809801/0407 ORIGINAL INSPECTED 5.) The method according to any one of claims 1 to 4, characterized characterized that the AufschluOmittel the sewage sludge or the sewage sludge ash during the high temperature treatment ^. 6.) The method according to any one of claims 1 to 5, characterized in that the high temperature treatment of the Sewage sludge or sewage sludge ash takes place in a fluidized bed furnace. 7.) The method according to any one of claims 1 to 5, characterized characterized that the high temperature treatment of the Sewage sludge or sewage sludge ash takes place in a rotary drum or deck oven. 8.) The method according to any one of claims 1 to 6, characterized in that the high-temperature treatment of the sewage sludge or the sewage sludge ash takes place in a melting chamber furnace. 9.) The method according to any one of claims 1 to 4, characterized characterized in that the sewage sludge ash and the disintegrating agent are briquetted and the briquettes of the Exposed to high temperature treatment by mixing in hot iron and steel slag. 809881/0487